#!/usr/local/bin/zsh -i
#
# Zsh calculator.  Understands most ordinary arithmetic expressions.
# Line editing and history are available. A blank line or `q' quits.
#
# Runs as a script or a function.  If used as a function, the history
# is remembered for reuse in a later call (and also currently in the
# shell's own history).  There are various problems using this as a
# script, so a function is recommended.
#
# The prompt shows a number for the current line.  The corresponding
# result can be referred to with $<line-no>, e.g.
#   1> 32 + 10
#   42
#   2> $1 ** 2
#   1764
# The set of remembered numbers is primed with anything given on the
# command line.  For example,
#   zcalc '2 * 16'
#   1> 32                     # printed by function
#   2> $1 + 2                 # typed by user
#   34
#   3> 
# Here, 32 is stored as $1.  This works in the obvious way for any
# number of arguments.
#
# If the mathfunc library is available, probably understands most system
# mathematical functions.  The left parenthesis must be adjacent to the
# end of the function name, to distinguish from shell parameters
# (translation: to prevent the maintainers from having to write proper
# lookahead parsing).  For example,
#   1> sqrt(2)
#   1.4142135623730951
# is right, but `sqrt (2)' will give you an error.
#
# You can do things with parameters like
#   1> pi = 4.0 * atan(1)
# too.  These go into global parameters, so be careful.  You can declare
# local variables, however:
#   1> local pi
# but note this can't appear on the same line as a calculation.  Don't
# use the variables listed in the `local' and `integer' lines below
# (translation: I can't be bothered to provide a sandbox).
#
# Some constants are already available: (case sensitive as always):
#   PI     pi, i.e. 3.1415926545897931
#   E      e, i.e. 2.7182818284590455
#
# You can also change the output base.
#   1> [#16]
#   1>
# Changes the default output to hexadecimal with numbers preceded by `16#'.
# Note the line isn't remembered.
#   2> [##16]
#   2>
# Change the default output base to hexadecimal with no prefix.
#   3> [#]
# Reset the default output base.
#
# This is based on the builtin feature that you can change the output base
# of a given expression.  For example,
#   1> [##16]  32 + 20 / 2
#   2A
#   2> 
# prints the result of the calculation in hexadecimal.
#
# You can't change the default input base, but the shell allows any small
# integer as a base:
#   1> 2#1111
#   15
#   2> [##13] 13#6 * 13#9
#   42
# and the standard C-like notation with a leading 0x for hexadecimal is
# also understood.  However, leading 0 for octal is not understood --- it's
# too confusing in a calculator.  Use 8#777 etc.
#
#
# To do:
# - separate zcalc history from shell history using arrays --- or allow
#   zsh to switch internally to and from array-based history.
# - allow setting number of decimal places for display, scientific notation, 
#   etc.

emulate -L zsh
setopt extendedglob

local line latest base defbase match mbegin mend psvar
integer num

zmodload -i zsh/mathfunc 2>/dev/null

: ${ZCALCPROMPT="%1v> "}

# Supply some constants.
float PI E
(( PI = 4 * atan(1), E = exp(1) ))

for (( num = 1; num <= $#; num++ )); do
  # Make sure all arguments have been evaluated.
  # The `$' before the second argv forces string rather than numeric
  # substitution.
  (( argv[$num] = $argv[$num] ))
  print "$num> $argv[$num]"
done

psvar[1]=$num
while vared -cehp "${(%)ZCALCPROMPT}" line; do
  [[ -z $line ]] && break
  # special cases
  # Set default base if `[#16]' or `[##16]' etc. on its own.
  # Unset it if `[#]' or `[##]'.
  if [[ $line = (#b)[[:blank:]]#('[#'(\#|)(<->|)']')[[:blank:]]#(*) ]]; then
    if [[ -z $match[4] ]]; then
      if [[ -z $match[3] ]]; then
	defbase=
      else
	defbase=$match[1]
      fi
      print -s -- $line
      line=
      continue
    else
      base=
    fi
  else
    base=$defbase
  fi
  # Exit if `q' on its own.
  [[ $line = [[:blank:]]#q[[:blank:]]# ]] && return 0

  print -s -- $line
  if [[ $line = [[:blank:]]#local([[:blank:]]##*|) ]]; then
    eval $line
  else
    # Latest value is stored as a string, because it might be floating
    # point or integer --- we don't know till after the evaluation, and
    # arrays always store scalars anyway.
    # 
    # Since it's a string, we'd better make sure we know which
    # base it's in, so don't change that until we actually print it.
    eval "latest=\$(( $line ))"
    argv[num++]=$latest
    psvar[1]=$num
    if [[ -z $base ]]; then
      print -- $latest
    else
      print -- $(( $base $latest ))
    fi
  fi
  line=
done

return 0