pratt: add parser
This is based on C's operator precedence rules
This commit is contained in:
commit
83c75de773
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@ -0,0 +1,22 @@
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CC = gcc
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CPPFLAGS = -Isrc/ -D_POSIX_C_SOURCE=200809L
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VPATH = src/
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CFLAGS = -Wall -Wextra -pedantic -Werror -std=c99
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USE_CLIMBING = 1
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SRC = \
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src/eval.c \
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BIN = pratt
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OBJ = $(SRC:.c=.o)
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.PHONY: all
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all: $(BIN)
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$(BIN):
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$(BIN): $(OBJ) src/pratt.o
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.PHONY: clean
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clean:
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$(RM) $(OBJ) # remove object files
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$(RM) $(BIN) # remove main program
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@ -0,0 +1,269 @@
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#include <ctype.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <string.h>
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#define UNREACHABLE() __builtin_unreachable()
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#define ARR_SIZE(Arr) (sizeof(Arr) / sizeof(*Arr))
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#define OP_STRING(...) (const char[]){__VA_ARGS__}
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#define OP_SIZE(...) (sizeof(OP_STRING(__VA_ARGS__)) - 1)
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typedef bool (nul_f)(const char **input, int *res, int until);
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typedef bool (left_f)(int lhs, const char **input, int *res, int until);
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// Define the different tokens
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enum token_kind {
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#define OP(Name, ...) Name,
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#include "operators.inc"
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};
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struct token {
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enum token_kind kind;
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int val; // Used for NUMBER
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};
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// Forward declare functions
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#define NulFunc(Name) \
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static nul_f eval_ ## Name ## _nul;
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#define LeftFunc(Name) \
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static left_f eval_ ## Name ## _left;
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#define PREFIX_POSTFIX(Name) \
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NulFunc(Name) \
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LeftFunc(Name)
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#define PREFIX(Name) \
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NulFunc(Name)
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#define PREFIX_INFIX(Name) \
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NulFunc(Name) \
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LeftFunc(Name)
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#define INFIX(Name) \
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LeftFunc(Name)
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#define TERN(Name) \
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LeftFunc(Name)
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#define PAREN(Name) \
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NulFunc(Name)
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#define NOT_OP(Name)
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# define OP(Name, NulPrio, LeftPrio, Type, ...) \
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Type(Name)
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#include "operators.inc"
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#undef NulFunc
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#undef LeftFunc
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// Symbol table
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static const struct {
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const char *op;
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const size_t op_len;
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const int nul_prio;
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const int left_prio;
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nul_f *const nul_func;
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left_f *const left_func;
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} ops[] = {
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#define NulFunc(Name) \
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eval_ ## Name ## _nul
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#define LeftFunc(Name) \
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eval_ ## Name ## _left
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#define PREFIX_POSTFIX(Name, NulPrio, LeftPrio, ...) \
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[Name] = {OP_STRING(__VA_ARGS__), OP_SIZE(__VA_ARGS__), NulPrio, LeftPrio, NulFunc(Name), LeftFunc(Name), },
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#define PREFIX(Name, NulPrio, LeftPrio, ...) \
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[Name] = {OP_STRING(__VA_ARGS__), OP_SIZE(__VA_ARGS__), NulPrio, LeftPrio, NulFunc(Name), NULL, },
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#define PREFIX_INFIX(Name, NulPrio, LeftPrio, ...) \
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[Name] = {OP_STRING(__VA_ARGS__), OP_SIZE(__VA_ARGS__), NulPrio, LeftPrio, NulFunc(Name), LeftFunc(Name), },
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#define INFIX(Name, NulPrio, LeftPrio, ...) \
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[Name] = {OP_STRING(__VA_ARGS__), OP_SIZE(__VA_ARGS__), NulPrio, LeftPrio, NULL, LeftFunc(Name), },
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#define TERN(Name, NulPrio, LeftPrio, ...) \
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[Name] = {OP_STRING(__VA_ARGS__), OP_SIZE(__VA_ARGS__), NulPrio, LeftPrio, NULL, LeftFunc(Name), },
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#define PAREN(Name, NulPrio, LeftPrio, ...) \
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[Name] = {OP_STRING(__VA_ARGS__), OP_SIZE(__VA_ARGS__), NulPrio, LeftPrio, NulFunc(Name), NULL, },
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#define NOT_OP(Name, NulPrio, LeftPrio, ...) \
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[Name] = {OP_STRING(__VA_ARGS__), OP_SIZE(__VA_ARGS__), NulPrio, LeftPrio, NULL, NULL, },
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# define OP(Name, NulPrio, LeftPrio, Type, Operator, /* Operator String */ ...) \
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Type(Name, NulPrio, LeftPrio, __VA_ARGS__)
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#include "operators.inc"
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#undef LeftFunc
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#undef NulFunc
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};
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// Lexing functions
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static void skip_whitespace(const char **input) {
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while (*input[0] && isspace(*input[0]))
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*input += 1; // Skip this character
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}
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static bool expect(enum token_kind expected, const char **input) {
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skip_whitespace(input);
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if (strncmp(*input, ops[expected].op, ops[expected].op_len) != 0)
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return false;
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*input += ops[expected].op_len;
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return true;
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}
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static size_t my_atoi(const char **input, int *val) {
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size_t len = 0;
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*val = 0; // Initialize its value
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while (isdigit((*input)[len]))
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{
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*val *= 10;
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*val += (*input)[len] - '0';
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len += 1;
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};
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return len;
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}
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static size_t lex_operator(const char **input, enum token_kind *op) {
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size_t best_len = 0;
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for (size_t i = 0; i < ARR_SIZE(ops); ++i)
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{
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if (ops[i].op_len <= best_len) // Only look at longer operators
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continue;
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if (strncmp(*input, ops[i].op, ops[i].op_len) == 0)
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{
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best_len = ops[i].op_len;
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*op = i;
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}
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}
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return best_len;
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}
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static size_t lex_token(const char **input, struct token *tok) {
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skip_whitespace(input);
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size_t len;
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if ((len = lex_operator(input, &tok->kind)))
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return len;
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// Assume that it is a number
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tok->kind = NUMBER;
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return my_atoi(input, &tok->val);
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}
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static bool parse_until_left(int lhs, const char **input, int *res, int prio) {
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struct token tok;
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size_t len = 0;
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while ((len = lex_token(input, &tok)) &&
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prio < ops[tok.kind].left_prio) {
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*input += len;
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left_f *left_func = ops[tok.kind].left_func;
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if (!left_func)
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return false; // Error: not a prefix operator
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if (!left_func(lhs, input, res, prio))
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return false; // Error: could not parse right-hand-side
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lhs = *res;
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}
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return true;
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}
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static bool parse_until(const char **input, int *res, int prio) {
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struct token tok;
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size_t len = 0;
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// Parse left token
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if (!(len = lex_token(input, &tok)))
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return false;
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// Assume prefix
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*input += len;
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if (tok.kind == NUMBER) {
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*res = tok.val;
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} else {
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nul_f *nul_func = ops[tok.kind].nul_func;
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if (!nul_func)
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return false; // Error: not a prefix operator
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nul_func(input, res, prio);
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}
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// Do left-loop
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return parse_until_left(*res, input, res, prio);
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}
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bool eval_string(const char *input, int *res) {
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if (!parse_until(&input, res, 0))
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return false;
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// Verify that only the expression exists
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skip_whitespace(&input);
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return *input == '\0';
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}
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#define NulFunc(Name) \
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static bool eval_ ## Name ## _nul( \
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const char **input, \
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int *res, \
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__attribute__((unused)) int until)
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#define LeftFunc(Name) \
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static bool eval_ ## Name ## _left( \
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int lhs, \
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const char **input, \
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int *res, \
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__attribute__((unused)) int until)
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#define PREFIX_POSTFIX(Name, NulPrio, LeftPrio, Operator) \
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LeftFunc(Name) { \
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return parse_until_left(lhs Operator, input, res, LeftPrio); \
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} \
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NulFunc(Name) { \
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if (!parse_until(input, res, NulPrio)) \
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return false; \
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Operator *res; \
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return true; \
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}
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#define PREFIX(Name, NulPrio, LeftPrio, Operator) \
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NulFunc(Name) { \
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if (!parse_until(input, res, NulPrio)) \
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return false; \
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*res = Operator *res; \
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return true; \
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}
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#define PREFIX_INFIX(Name, NulPrio, LeftPrio, Operator) \
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LeftFunc(Name) { \
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if (!parse_until(input, res, LeftPrio)) \
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return false; \
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*res = lhs Operator *res; \
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return true; \
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} \
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NulFunc(Name) { \
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if (!parse_until(input, res, NulPrio)) \
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return false; \
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*res = Operator *res; \
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return true; \
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}
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#define INFIX(Name, NulPrio, LeftPrio, Operator) \
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LeftFunc(Name) { \
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if (!parse_until(input, res, LeftPrio)) \
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return false; \
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*res = lhs Operator *res; \
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return true; \
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}
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#define TERN(Name, NulPrio, LeftPrio, Operator) \
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LeftFunc(Name) { \
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int true_val; \
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if (!parse_until(input, &true_val, 0) || !expect(COLON, input)) \
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return false; \
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int false_val; \
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if (!parse_until(input, &false_val, until)) \
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return false; \
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*res = (lhs ? true_val : false_val); \
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return true; \
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}
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#define PAREN(Name, NulPrio, LeftPrio, Operator) \
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NulFunc(Name) { \
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if (!parse_until(input, res, 0)) \
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return false; \
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return expect(R_PAREN, input); \
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}
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#define NOT_OP(Name, NulPrio, LeftPrio, Operator) /* Nothing */
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# define OP(Name, NulPrio, LeftPrio, Type, Operator, ...) \
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Type(Name, NulPrio, LeftPrio, Operator)
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#include "operators.inc"
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#undef LeftFunc
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#undef NulFunc
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@ -0,0 +1,8 @@
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#ifndef ONCE_H
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#define ONCE_H
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#include <stdbool.h>
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bool eval_string(const char *input, int *res);
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#endif /* !ONCE_H */
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/*
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* 10 '?:' ternary (set to 0 in middle)
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*
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* Do not use any assignation yet
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*/
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#ifndef OP
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# define OP(Name, NulPrio, LeftPrio, Type, Operator, /* Operator String */ ...)
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#endif
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// Simple operators
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OP( PLUS_PLUS, 120, 110, PREFIX_POSTFIX, ++, '+', '+', 0)
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OP(MINUS_MINUS, 120, 110, PREFIX_POSTFIX, --, '-', '-', 0)
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OP( NOT, 120, -1, PREFIX, !, '!', 0)
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OP( BIT_NOT, 120, -1, PREFIX, ~, '~', 0)
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OP( PLUS, 110, 90, PREFIX_INFIX, +, '+', 0)
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OP( MINUS, 110, 90, PREFIX_INFIX, -, '-', 0)
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OP( TIMES, -1, 100, INFIX, *, '*', 0)
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OP( DIVIDES, -1, 100, INFIX, /, '/', 0)
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OP( MODULO, -1, 100, INFIX, %, '%', 0)
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OP( LEFT_SHIFT, -1, 80, INFIX, <<, '<', '<', 0)
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OP( RIGHT_SHIFT, -1, 80, INFIX, >>, '>', '>', 0)
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OP( EQUAL, -1, 70, INFIX, ==, '=', '=', 0)
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OP( NOT_EQUAL, -1, 70, INFIX, !=, '!', '=', 0)
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OP( BIT_AND, -1, 60, INFIX, &, '&', 0)
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OP( BIT_XOR, -1, 50, INFIX, ^, '^', 0)
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OP( BIT_OR, -1, 40, INFIX, |, '|', 0)
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OP( AND, -1, 30, INFIX, &&, '&', '&', 0)
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OP( OR, -1, 20, INFIX, ||, '|', '|', 0)
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// Special operators
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OP( TERNARY, -1, 10, TERN, PLACEHOLDER, '?', 0)
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OP( COLON, -1, -1, NOT_OP, PLACEHOLDER, ':', 0)
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OP( L_PAREN, 0, 0, PAREN, PLACEHOLDER, '(', 0)
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OP( R_PAREN, -1, -1, NOT_OP, PLACEHOLDER, ')', 0)
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// Special tokens
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OP( NUMBER, 0, -1, NOT_OP, PLACEHOLDER, 0)
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#undef OP
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#undef PREFIX_POSTFIX
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#undef PREFIX
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#undef PREFIX_INFIX
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#undef INFIX
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#undef TERN
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#undef PAREN
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#undef NOT_OP
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@ -0,0 +1,28 @@
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#include <stdio.h>
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#include <stdlib.h>
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#include "eval.h"
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int main(void)
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{
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char *line = NULL;
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size_t size = 0;
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ssize_t ret = 0;
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while ((getline(&line, &size, stdin)) > 0)
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{
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int res;
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if (!eval_string(line, &res))
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{
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fputs("Could not parse input\n", stderr);
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ret = 1;
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continue;
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}
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printf("%d\n", res);
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}
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free(line);
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return ret;
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}
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