A hack to simulate a REPL for VOC

repl-voc.sh

#!/bin/bash
# For arrow-keys history and other cmdline goodies, install rlwrap and replace
# the first line by:  #!/usr/bin/rlwrap bash

# This is a hack to simulate a REPL for VOC (http://pybee.org/voc)
#
# Behind the scenes, every time you try a new expression it appends it to a temporary
# file, recompiles it and re-runs it, omitting the previous output.
#
# This has the caveat that if some expression you enter raises an exception,
# it will be always raised no matter you give in the next input.
#
# This is an experiment I did because I wanted a quick way of trying things without
# having to create a bunch of files everytime.

VOC_DIR=../voc

abort() {
    echo "$*"; exit 1;
}

usage() {
    abort "Usage: $(basename $0) [-h|--help]"
}

require() {
    type $1 >/dev/null 2>/dev/null
}

classpath=.
while [ "${1#-}" != "$1" ]; do
    case "$1" in
        -h|--help) usage;;
        -cp|--classpath) classpath="$2:."; shift;;
        *) usage;;
    esac
    shift
done

pyfile="_tempfile.py"
basefile=$(basename $pyfile .py)
workdir="$(dirname $0)"

(cd $VOC_DIR && ant java)
cd "$workdir" || abort "Could not enter directory $workdir"

> $pyfile

lines_previous_output=0
while read -p '>>> ' line
do
    if echo "$line" | grep -vq -E '[^=]=[^=]|^from|^import|^print|^$|^raise |^del |^try:' && echo "$line" | grep -vq '^print'; then
        line="_ = ${line}; print(repr(_))"
    fi
    echo "$line" >> $pyfile
    voc $pyfile
    output=$(java -cp $VOC_DIR/dist/python-java-support.jar:$classpath python.${basefile})
    java_status=$?
    if [ "$output" != "" ]; then
        if [ "$lines_previous_output" != "0" ]; then
            echo "$output" | sed "1,$lines_previous_output d"
        else
            echo "$output"
        fi
        lines_previous_output=$(echo "$output" | wc -l)
    fi
    if [ $java_status != 0 ]; then
        sed -i '$d' $pyfile
    fi
done