diff options
Diffstat (limited to 'ev1')
| -rwxr-xr-x | ev1 | 115 |
1 files changed, 115 insertions, 0 deletions
@@ -0,0 +1,115 @@ +#!/usr/bin/env awk -f + +# an evaluator of code: scanner, parser and bytecode vm. + +BEGIN { + # The prec array contains the precedence level of binary operators. + prec["="] = prec["=="] = prec["!="] = prec["<"] = prec["<="] = prec[">"] = prec[">="] = 1 + prec["+="] = prec["-="] = prec["*="] = prec["/="] = prec["%="] = prec["^="] = 1 + prec["+"] = prec["-"] = 2 + prec["*"] = prec["/"] = prec["%"] = 3 + prec["^"] = 4 + # The rigth array contains binary operators which are right associative. + right["="] = right["+="] = right["-="] = right["*="] = right["/="] = right["%="] = right["^="] = 1 + right["^"] = 1 + start[")"] = "(" + start["}"] = "{" + start["]"] = "[" + + + sp = pc = 0 # sp: stack pointer, pc: program counter. + split("", code) + split("", stack) + split("", sym) + printf "> " +} +{ + line = $0 + parse() + run() + printf "> " +} + +function scan() { + ptok = tok + sub(/^[ \t]+/, "", line) + if (match(line, /^[0-9]([.0-9]*(e[+-]*)*[0-9])*/)) { # Literal number + tok = "d" substr(line, 1, RLENGTH) + } else if (match(line, /^([-=+|&]{2}|![=~]|[<>+-*\/^%]=)/)) { # Operator (2 chars) + tok = substr(line, 1, RLENGTH) + } else if (match(line, /^([][}{)(,+-=?:]|[*\/รท\^])/)) { # Operator (1 char) + tok = substr(line, 1, RLENGTH) + } else if (match(line, /^[A-Za-z_][A-Za-z_0-9]*/)) { # Identifier + tok = "v" substr(line, 1, RLENGTH) + } else if (match(line, /^"(\\.|[^\\"])*"/)) { # Literal string + tok = "s" substr(line, 2, RLENGTH-2) + } else { # Bad token + tok = "b" substr(line, 1, 1) + } + line = substr(line, RLENGTH+1) + return RLENGTH +} + +# TODO: unary operators, flow contror +function parse( ops, sl, i, b) { + b = i = length(code) + while (scan() > 0) { + if (tok ~ /[({[]/) { + ops[++sl] = tok + } else if (tok in start) { + while (sl && ops[sl] != start[tok]) code[i++] = ops[sl--] + sl-- + } else if (tok in prec) { + # print "tok:" tok " ptok:" ptok + if (tok ~ /[+-*\/%^]?=/ && ptok ~ /^v/) sub(/^v/, "p", code[i-1]) # mutate var to pointer for assign + # Test precedence against ops, or associativity if same precedence. + while (sl && (prec[tok] < prec[ops[sl]] || prec[tok] == prec[ops[sl]] && !(ops[sl] in right))) { + code[i++] = ops[sl--] + } + ops[++sl] = tok + } else { + code[i++] = tok + } + } + while (sl) code[i++] = ops[sl--] + for (j = b; j < i; j++) printf("%s ", code[j]); print "" +} + +# TODO: if, while, function +# Feel like being a stack machine. +function run( c, i, l, t) { + cl = length(code) + while (pc < cl) { + c = code[pc] + if (c == "+") { + stack[--sp] = stack[sp-1] + stack[sp] + } else if (c == "-") { + stack[--sp] = stack[sp-1] - stack[sp] + } else if (c == "*") { + stack[--sp] = stack[sp-1] * stack[sp] + } else if (c == "/") { + stack[--sp] = stack[sp-1] / stack[sp] + } else if (c == "^") { + stack[--sp] = stack[sp-1] ^ stack[sp] + } else if (c == "=") { + stack[--sp] = sym[substr(stack[sp-1], 2)] = stack[sp] + } else if (c == "+=") { + stack[--sp] = sym[substr(stack[sp-1], 2)] += stack[sp] + } else if (c ~ /^p/) { + stack[++sp] = c + } else if (c ~ /^v/) { + stack[++sp] = sym[substr(c, 2)] + } else if (c ~ /^[d]/) { + stack[++sp] = 0 + substr(c, 2) + } else { + print "run: invalid instruction " c + return + } + # printf "c" pc ":%s", c; for (i = 1; i <= sp; i++) printf " " i ":" stack[i]; print "" + # for (i in sym) print "sym[" i "]=" sym[i] + pc++ + } + print sym["_"] = stack[sp--] + print "sp: " sp ", len(stack): " length(stack) + # for (i = sp; j in stack; i++) delete stack[i] +} |