def p_for(self, p):
'loop_i : FOR LPAREN assign_e SEMICOLON expr SEMICOLON assign_e RPAREN instr'
pre = syntax.evaluation(p[3])
mid = p[5]
post = syntax.evaluation(p[7])
body = p[9]
p[0] = syntax.block_statement([pre, syntax.while_loop(mid, post, body, p.lexpos(1))])
def p_expr_i(self, p):
'expr_i : expr SEMICOLON'
p[0] = syntax.evaluation(p[1])
