Algebraic expressions

  • Difficulty: 002/100
  • Author: jeremy theler
  • Keywords: PRINT, =, expressions, TEXT,

These examples show how algebraic expressions work in wasora, which is basically as they should. The basic operators are composed by the four basic operations +, -, * and / plus the exponentation operator ^. Parenthesis also work as expected, and can be nested up to any level. Other operators such as comparisons and logicals are introduced in other examples.

expr.was

Expressions works as expected. If you find one case where they do not, please report it to the author of wasora.

# algebraic expressions do whatever one expects them to do
# thus a should evaluate to 7
a = 1 + 2*3
# and b should evaluate to 9
b = (1+2) * 3

# expressions can contain variables and functions, whose
# arguments may be expressions themselves, and so on
c = (1 + sin(pi/4)^(5/2))/(1 - log(abs(a-b)))

PRINT %g a b c

# when an expression appears as an argument of a keyword and
# contains spaces it should be written within double quotes
PRINT %g 1 -1 "1 -1"
$ wasora expr.was
7   9   4.62909
1   -1  0
$ 

By default PRINT introduces a tab between its arguments. This behavior can be changed with the SEPARATOR keyword.

hoc.was

When PRINT finds a new argument, it tries to evaluate it. If it does not make any sense, then wasora treats it as a text string. However, if a certain argument that constitutes a valid algebraic expression is to be treated as a text, it should be prefixed with the TEXT keyword, as the following example illustrates.

# actually arguments of the PRINT keyword may be either text
# strings, scalar expresions, vectors or matrices (more about
# these latter two issues in more complex examples)

# the example of Kernigham & Ritchie HOC code
PRINT TEXT "1+2*sin(0.7)" "=" %.6f 1+2*sin(0.7)
$ wasora hoc.was
1+2*sin(0.7)    =   2.288435
$ 

Note that the double quotes are not needed, as there are no spaces in 1+2*sin(0.7). However, it is a good practice to leave them for text strings, as one might want to add extra spaces in the future.