test

library(shiny)

Warning: package 'shiny' was built under R version 4.4.3

# Safely evaluate expressions like "1/2", "8/4", etc.
try_eval <- function(expr_str) {
  tryCatch({
    result <- eval(parse(text = expr_str))
    if (is.numeric(result)) result else NA
  }, error = function(e) NA)
}

ui <- fluidPage(
  titlePanel("Prime Checker and Factorial Calculator"),

  # JS: Allow Enter key to submit the form
  tags$script(HTML("
    $(document).on('keypress', function (e) {
      if (e.which == 13 && $('#user_input').is(':focus')) {
        setTimeout(function() {
          $('#check').click();
        }, 50);
      }
    });
  ")),

  # Responsive CSS styling with top padding
  tags$style(HTML("
    body {
      font-family: 'Segoe UI', 'Helvetica Neue', sans-serif;
      font-size: 16px;
      text-align: center;
      padding-top: 5vh;
    }
    .centered {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      margin-top: 20px;
    }
    #user_input {
      font-size: 17px;
      padding: 6px;
      width: 200px;
      text-align: center;
    }
    #check {
      font-size: 17px;
      height: 38px;
      margin-left: 10px;
    }
    #prime_text, #bigfact {
      font-size: 17px;
      text-align: center;
    }
    #bigfact {
      max-height: 100px;
      max-width: 600px;
      overflow-x: auto;
      overflow-y: auto;
      white-space: nowrap;
      border: 1px solid #ddd;
      padding: 10px;
      background-color: #f9f9f9;
      font-weight: normal;
      margin: 10px auto 0 auto;
    }
  ")),

  # Main layout with centered input row
  div(class = "centered",
    tags$div(
      style = "display: flex; align-items: center; gap: 10px;",
      tags$label("Enter a number:", `for` = "user_input"),
      tags$input(
        id = "user_input",
        type = "text",
        value = ""
      ),
      actionButton("check", "Submit")
    ),
    br(), br(),
    textOutput("prime_text"),
    uiOutput("factorial_text")
  )
)

server <- function(input, output, session) {

  # Clear output when input is cleared
  observe({
    if (input$user_input == "") {
      output$prime_text <- renderText("")
      output$factorial_text <- renderUI(NULL)
    }
  })

  observeEvent(input$check, {
    input_raw <- input$user_input

    if (input_raw == "") {
      output$prime_text <- renderText("")
      output$factorial_text <- renderUI(NULL)
      return()
    }

    # Evaluate safely (supports fractions like 8/4)
    num <- try_eval(input_raw)

    if (is.na(num)) {
      output$prime_text <- renderText("That's not a number! Try again.")
      output$factorial_text <- renderUI(NULL)
      return()
    }

    # Prime checker logic
    is_prime <- function(n) {
      if (n <= 1) return(FALSE)
      if (n == 2 || n == 3) return(TRUE)
      if (n %% 2 == 0) return(FALSE)
      for (i in 3:floor(sqrt(n))) {
        if (n %% i == 0) return(FALSE)
      }
      return(TRUE)
    }

    # Handle decimals or negatives
    if (num != floor(num) || num < 0) {
      output$prime_text <- renderText("❌ That's NOT a prime number!")
      output$factorial_text <- renderUI("Undefined. Factorial is UNDEFINED.")
    } else {
      # Prime result
      prime_result <- if (is_prime(num)) {
        "✔️ That's a prime number!"
      } else {
        "❌ That's NOT a prime number!"
      }
      output$prime_text <- renderText(prime_result)

      # Factorial or fallback
      fact <- factorial(num)

      if (is.infinite(fact)) {
        approx_val <- exp(lgamma(num + 1))
        if (is.infinite(approx_val)) {
          output$factorial_text <- renderUI("Factorial too large to approximate.")
        } else {
          approx_fact <- format(approx_val, scientific = TRUE)
          output$factorial_text <- renderUI({
            paste0("Number exceeds computational limits. Factorial result is approximate:\n", approx_fact)
          })
        }
      } else {
        fact_str <- format(fact, scientific = FALSE)
        fact_exp <- format(fact, scientific = TRUE)

        if (num > 20 || nchar(fact_str) > 24) {
          output$factorial_text <- renderUI({
            tagList(
              paste0("Factorial (short): ", fact_exp, "\n\n"),
              div(id = "bigfact", fact_str)
            )
          })
        } else {
          output$factorial_text <- renderUI({
            paste0("Factorial: ", fact_str)
          })
        }
      }
    }
  })
}

# Launch the app
shinyApp(ui = ui, server = server)

Shiny applications not supported in static R Markdown documents