72 lines
1.4 KiB
C
72 lines
1.4 KiB
C
#include "eval.h"
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#define UNREACHABLE() __builtin_unreachable()
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static int my_pow(int lhs, int rhs)
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{
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if (!rhs)
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return 1;
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int rec = my_pow(lhs * lhs, rhs / 2);
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if (rhs & 1)
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rec *= lhs;
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return rec;
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}
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static int my_fact(int num)
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{
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int ret = 1;
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while (num > 1)
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ret *= num--;
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return ret;
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}
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static int eval_unop(const struct unop_node *un_op)
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{
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switch (un_op->op)
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{
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case UNOP_IDENTITY:
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return eval_ast(un_op->tree);
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case UNOP_NEGATE:
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return -eval_ast(un_op->tree);
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case UNOP_FACT:
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return my_fact(eval_ast(un_op->tree));
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default:
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UNREACHABLE();
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}
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}
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static int eval_binop(const struct binop_node *bin_op)
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{
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#define EVAL_OP(OP, TREE) (eval_ast((TREE)->lhs) OP eval_ast((TREE)->rhs))
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switch (bin_op->op)
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{
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case BINOP_PLUS:
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return EVAL_OP(+, bin_op);
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case BINOP_MINUS:
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return EVAL_OP(-, bin_op);
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case BINOP_TIMES:
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return EVAL_OP(*, bin_op);
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case BINOP_DIVIDES:
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return EVAL_OP(/, bin_op);
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case BINOP_POW:
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return my_pow(eval_ast(bin_op->lhs), eval_ast(bin_op->rhs));
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default:
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UNREACHABLE();
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}
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#undef EVAL_OP
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}
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int eval_ast(const struct ast_node *ast)
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{
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switch (ast->kind)
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{
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case NODE_NUM:
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return ast->val.num;
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case NODE_UNOP:
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return eval_unop(&ast->val.un_op);
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case NODE_BINOP:
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return eval_binop(&ast->val.bin_op);
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}
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UNREACHABLE();
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}
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