pratt: add parser

This is based on C's operator precedence rules

Makefile

@@ -0,0 +1,22 @@
+CC = gcc
+CPPFLAGS = -Isrc/ -D_POSIX_C_SOURCE=200809L
+VPATH = src/
+CFLAGS = -Wall -Wextra -pedantic -Werror -std=c99
+USE_CLIMBING = 1
+
+SRC = \
+    src/eval.c \
+
+BIN = pratt
+OBJ = $(SRC:.c=.o)
+
+.PHONY: all
+all: $(BIN)
+
+$(BIN):
+$(BIN): $(OBJ) src/pratt.o
+
+.PHONY: clean
+clean:
+	$(RM) $(OBJ) # remove object files
+	$(RM) $(BIN) # remove main program