comma

I have discovered that wrapping different statements in parentheses will return the last one: (34892,47691876297,2000) => 2000 ('test',73,document.createElement('p')) => <p></p> And I also found out that all the statements are executed anyway: (console.log('test'), console.log('test2'), console.log('test3'), 6) Will log: test test2 test3 And the result will be 6. However, I've also found that some statements can't be used: (throw new Error(), 10) => SyntaxError: Unexpected token throw (if (1) console.log('test'), 5) => SyntaxError: Unexpected token if So, what is the point of this parenthesis

This question already has an answer here: How does the Comma Operator work 9 answers C++ What does 'int x = (anyInt1, anyInt2);' mean? [duplicate] 2 answers I've just come across code that essentially does the following: int a = (1, 2, 3); I've never seen this notation before. What does it mean? This is the comma operator : evaluation of a, b first causes a to be evaluated, then b , and the result is that of b . int a = (1, 2, 3); first evaluates 1 , then 2 , finally 3 , and uses that last 3 to initialise a . It is useless here, but it can be useful when the left operand of , has side effects

What's the best Ruby/Rails way to allow users to use decimals or commas when entering a number into a form? In other words, I would like the user be able to enter 2,000.99 and not get 2.00 in my database. Is there a best practice for this? -- Update --- Does gsub work with floats or bigintegers? Or does rails automatically cut the number off at the , when entering floats or ints into a form? I tried using self.price.gsub(",", "") but get "undefined method `gsub' for 8:Fixnum" where 8 is whatever number I entered in the form. I had a similar problem trying to use localized content inside forms.

I'm walking through basic tutorials for matplotlib, and the example code that I'm working on is: import numpy as np import matplotlib.pylab as plt x=[1,2,3,4] y=[5,6,7,8] line, = plt.plot(x,y,'-') plt.show() Does anyone know what the comma after line ( line,=plt.plot(x,y,'-') ) means? I thought it was a typo but obviously the whole code doesn't work if I omit the comma. plt.plot returns a list of the Line2D objects plotted, even if you plot only one line. That comma is unpacking the single value into line . ex a, b = [1, 2] a, = [1, ] The plot method returns objects that contain information

#include<stdio.h> main() { int i; for(i=0;i<0,5;i++) printf("%d\n",i); } I am unable to understand i<0,5 part in the condition of for loop. Even if I make it i>0,5 , there's no change in output. How does this work? Comma operator evaluates i<0 Or i>0 and ignores. Hence, it's always the 5 that's present in the condition. So it's equivalent to: for(i=0;5;i++) On topic The comma operator will always yield the last value in the comma separated list. Basically it's a binary operator that evaluates the left hand value but discards it, then evaluates the right hand value and returns it. If you chain

In the following type of code is there a sequence point between each variable construction, or is the result undefined? int a = 0; int b = a++, c = a++; I wasn't able to find in the standard a specific reference to a sequence point here. Does that mean it is undefined, or just that I failed in my search? The completion of an expression is a sequence point, but does the above initialization also count? I believe behavior is well-defined because of 8[dcl.decl]/3 Each init-declarator in a declaration is analyzed separately as if it was in a declaration by itself. Which is even additionally