file-exists | Check if filepath exists and is a file | File Utils library

I am currently working on a project where I am reading in contents from a file, line by line. I would like to check if the file can be opened or is present before I do this. Something like checking the return contents of fopen() in C++, but in Scheme.

Thus far I have:

I just discovered an error in my model where I create a population with a household-size distribution and dependent age distribution. My problem is that my procedure doesn't seem to assign the probabilities for each outcome correctly when deciding the age. I am supposed to have 16% elderly but my model gives me 3% (of tot population).

I think this has to do with the internal order of the procedure, as elderly are assigned last. See below code.

Procedure for assigning household-size:

I am struggling with a simple Makefile.

The simplified version looks something like this:

I'm working in a UWP app, at some point, the user has the chance to save an image (done) by now I only let the user know that the save operation was done by a "messageDialog", this is my code:

I have an Angular 9 application that works fine with ng serve, but when I build it and run under nginx if the user presses F5 refresh on any page I get a 404 not found page from nginx. This happens because the Angular route is not a valid URL page.

How to tell nginx NOT to check that the page exists, and let Angular handle the routing?

I tried with this with no success.

I have problem with my code, I'm not able to save newline using binary port, I want to write unit test for my Scheme implementation but I'm not able to figure out why I got this results also in Gambit and Kawa (Gauche and Guile fail to run the code, because of missing procedures).

Sometimes I like to output some text with (format t ..).
To prevent long unreadable format-strings in source code, and get the output easily aligned, I use (format t (concatenate 'string ....).

Example:

While trying to work through cl-sdl2-tutorial, I'm having trouble loading a bitmap due to a wrong current working directory.
I'd like to get a proper solution to the problem using relative path names.

A minimal working example:
Having modified the code of example two from above mentioned tutorial.

I am trying to write a batch script that will loop through a list of file names and:

1. Attempt to create that file
2. Check if the creation was successful, and if not, try again after a few seconds

This is as far as I've gotten, which borrows from this question. However, it will only check and create file1.txt, not file2.txt or file3.txt. Then it will create a file "%A". Why is it only looping through the first file, and where is "%A" coming from?

I assume it is something to do with how I'm using the variable %A. Especially because if I manually type this out in the command prompt, instead of a batch file, and using %A instead of %%A, it works correctly.