V.6 Numbers

Arithmetic is not done directly by the Tcl interpreter. It is done by calling the C library using the expr command on arthmetic expressions. The detailed parsing rules for arithmetic expressions depend on the particular Unix implementation, but they are more or less like in C.

Here are some examples:

# integer division truncates
% expr {7 / 2}
3

# the percent sign is used to compute integer remainder
% expr {7 % 2} 
1

# floating point propagates
% expr {7.0 / 2}
3.5

% expr {sin(.5) + cos(.9)}
1.10103550687

% # a zero in front of number means to interpret as octal
% expr {017 + 01}
16

% # a 0x in front means to interpret as hex
% expr {0xA + 1}
11

% # numbers can be treated like strings!
% string length 100.34
6
% string range 100.34 0 2
100

More: http://www.tcl.tk/man/tcl8.4/TclCmd/expr.htm 

 

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Reference

Here are the numeric functions included in Tcl. (Details may vary depending on your Unix implementation of expr.)

• abs(x)
• asin(x)
• acos(x)
• atan(x)
• atan2(y,x)
  atan2 returns the angle theta of the polar coordinates returned when (x,y) is converted to (r, theta).
• ceil(x)
• cos(x)
• cosh(x)
• double(x)
  returns x as a double or floating point.
• exp(x)
  returns e^x
• floor(x)
• fmod(x,y)
  returns the floating point remainder of x/y.
• hypot(x,y)
  returns the square root of the sum of x squared plus y squared, the length of the line from (0,0) to (x,y).
• int(x)
  truncates x to an integer.
• log(x)
  returns the natural log of x.
• log10(x)
  returns log base 10 of x.
• pow(x,y)
  returns x to the y power.
• rand() 
• round(x)
• sin(x)
• sinh(x)
• sqrt(x)
• tan(x)
• tanh(x)
• wide(x)

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based on Tcl for Web Nerds