Seed7 Program: Calc7

Calc7

Calc7 is the Seed7 calculator. It works like a read-eval-print loop (REPL).

Calc7 is interactive program that reads single expressions, evaluates them and writes the results. Calc7 can be called from a command window with:

s7 calc7

Calc7 requests user input with the prompt:

calculate?

The user can enter an expression (on this page user input is displayed in green):

calculate? 1+2*3

Pressing Return (or Enter) starts the evaluation. Calc7 responds with the result:

The commands quit and exit can be used to leave calc7. An input line can be edited with the following keys:

	Backspace		Delete the charater to the left.
	Delete		Delete the current character.
	Home		Jump to the first position.
	End		Jump behind the last position.
	←, →		Move cursor left and right.
	↑, ↓		Get previous input lines from the command history.

Calc7 accepts arbitrary complex Seed7 expressions:

calculate? length(str(-((1+2)*4)**12))
14

The expressions can use the types boolean, integer, bigInteger, rational, bigRational, float, complex, char, string, array, hash, set, time and duration:

calculate? 2 + 2 >= 2 * 2
TRUE
calculate? "hi" mult 5
hihihihihi
calculate? 2.5**2
6.25
calculate? 1/19
0.(052631578947368421)
calculate? time(NOW)
2014-07-30 12:56:13.915252 UTC+2 (DST)

Syntax errors are shown as follows:

calculate? "abc
*** STRING(17):25: String literal exceeds source line
      writeln("abc);
--------------------^
*** STRING(18):46: ")" expected found "exception"
    exception
-------------^
*** 2 errors found

Computation errors are shown with the name of the exception:

calculate? 1 div 0
NUMERIC_ERROR

If the result of an integer expression is too big or too small the exception OVERFLOW_ERROR is raised:

calculate? 4000000000 * 3000000000
OVERFLOW_ERROR

To avoid an overflow the computation can be done with bigInteger:

calculate? 4000000000_ * 3000000000_
12000000000000000000